Mitochondrial disorders

Extremely variable clinic and genetic features characterize Mitochondrial Encephalomyopathy Disorders (MED). Pathogenic mitochondrial DNA (mtDNA) defects can be divided into large-scale rearrangements and single point mutations. Clinical manifestations become evident when a threshold percentage of the total mtDNA is mutated. In some MED, the "mutant load" in an affected tissue is directly related to the severity of the phenotype. However, the clinical phenotype is not simply a direct consequence of the relative abundance of mutated mtDNA. Other factors, such as nuclear background, can contribute to the disease process, resulting in a wide range of phenotypes caused by the same mutation. Using Affymetrix oligonucleotide cDNA microarrays (HG-U133A), we studied the gene expression profile of muscle tissue biopsies obtained from 12 MED patients (4 common 4977-bp deleted mtDNA and 8 A3243G: 4 PEO and 4 MELAS phenotypes) compared with age-matched healthy individuals. Keywords = mtDNA mutation Keywords = muscle biopsy Keywords = human Keywords = mitochondrial disease Keywords: other